if i understand correctly, you are searching for keyPressed(),

http://processing.org/reference/keyPressed_.html

Useful trick: go to the Reference page, and use the find feature of your browser (usually via Ctrl+F) to search something there. If you don't find it, simplify. Eg. searching key would show keyPressed, keyReleased and keyTyped, the latest might be the closest of what you search.

thank you  phi.lho